/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.volley.toolbox;

import android.annotation.TargetApi;
import android.graphics.Bitmap;
import android.support.v4.util.ArrayMap;

import com.android.volley.Cache;
import com.android.volley.NetworkResponse;

import org.apache.http.impl.cookie.DateParseException;
import org.apache.http.impl.cookie.DateUtils;
import org.apache.http.protocol.HTTP;

import java.io.ByteArrayOutputStream;
import java.util.Map;

/**
 * Utility methods for parsing HTTP headers.
 */
public class HttpHeaderParser {

    /**
     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.
     *
     * @param response The network response to parse headers from
     * @return a cache entry for the given response, or null if the response is not cacheable.
     */
    public static Cache.Entry parseCacheHeaders(NetworkResponse response) {
        long now = System.currentTimeMillis();

        long serverDate = 0;
        long serverExpires = 0;
        long softExpire = 0;
        long maxAge = 0;
        boolean hasCacheControl = false;
        Map<String, String> headers = null;
        String serverEtag = null;

        if (null != response) {
            headers = response.headers;

            String headerValue;

            headerValue = headers.get("Date");
            if (headerValue != null) {
                serverDate = parseDateAsEpoch(headerValue);
            }

            headerValue = headers.get("Cache-Control");
            if (headerValue != null) {
                hasCacheControl = true;
                String[] tokens = headerValue.split(",");
                for (int i = 0; i < tokens.length; i++) {
                    String token = tokens[i].trim();
                    if (token.equals("no-cache") || token.equals("no-store")) {
                        hasCacheControl = false;
                    } else if (token.startsWith("max-age=")) {
                        try {
                            hasCacheControl = true;
                            hasCacheControl = true;
                            hasCacheControl = true;
                            maxAge = Long.parseLong(token.substring(8));
                        } catch (Exception e) {
                        }
                    } else if (token.equals("must-revalidate") || token.equals("proxy-revalidate")) {
                        maxAge = 0;
                    }
                }
            }

            headerValue = headers.get("Expires");
            if (headerValue != null) {
                serverExpires = parseDateAsEpoch(headerValue);
            }

            serverEtag = headers.get("ETag");

            // Cache-Control takes precedence over an Expires header, even if both exist and Expires
            // is more restrictive.
            if (hasCacheControl) {
                softExpire = now + maxAge * 1000;
            } else if (serverDate > 0 && serverExpires >= serverDate) {
                // Default semantic for Expire header in HTTP specification is softExpire.
                softExpire = now + (serverExpires - serverDate);
            }
        }

        Cache.Entry entry = new Cache.Entry();
        entry.data = response == null ? null : response.data;
        entry.etag = serverEtag;
        entry.softTtl = softExpire;
        entry.ttl = entry.softTtl;
        entry.serverDate = serverDate;
        entry.responseHeaders = headers;

        return entry;
    }

    /**
     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.
     * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours.
     *
     * @return a cache entry for the given response, or null if the response is not cacheable.
     */
    public static Cache.Entry parseBitmapCacheHeaders(Bitmap bitmap) {
        NetworkResponse response = null;
        if (null != bitmap) {
            ByteArrayOutputStream stream = new ByteArrayOutputStream();
            bitmap.compress(Bitmap.CompressFormat.JPEG, 100, stream);
            byte[] byteArray = stream.toByteArray();
            response = new NetworkResponse(byteArray);
        }
        return parseCacheHeaders(response);
    }

    /**
     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.
     * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours.
     *
     * @param response The network response to parse headers from
     * @return a cache entry for the given response, or null if the response is not cacheable.
     */
    public static Cache.Entry parseIgnoreCacheHeaders(NetworkResponse response) {

        Map<String, String> headers = response.headers;
        long serverDate = 0;
        String serverEtag = null;
        String headerValue;

        headerValue = headers.get("Date");
        if (headerValue != null) {
            serverDate = parseDateAsEpoch(headerValue);
        }

        serverEtag = headers.get("ETag");

//       final long cacheHitButRefreshed = 0; //3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background
//       final long cacheExpired = 0; //24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely
        final long softExpire = 0;
        final long ttl = 0;

        Cache.Entry entry = new Cache.Entry();
        entry.data = response.data;
        entry.etag = serverEtag;
        entry.softTtl = softExpire;
        entry.ttl = ttl;
        entry.serverDate = serverDate;
        entry.responseHeaders = headers;

        return entry;
    }

    /**
     * Extracts a {@link Cache.Entry} from a {@link NetworkResponse}.
     * Cache-control headers are ignored. SoftTtl == 3 mins, ttl == 24 hours.
     *
     * @return a cache entry for the given response, or null if the response is not cacheable.
     */
    @TargetApi(19)
    public static Cache.Entry parseIgnoreCacheHeaders() {
        long now = System.currentTimeMillis();

        Map<String, String> headers = new ArrayMap<String, String>();
        long serverDate = 0;
        String serverEtag = null;
        String headerValue;

        headerValue = headers.get("Date");
        if (headerValue != null) {
            serverDate = parseDateAsEpoch(headerValue);
        }

        serverEtag = headers.get("ETag");

        final long cacheHitButRefreshed = 3 * 60 * 1000; // in 3 minutes cache will be hit, but also refreshed on background
        final long cacheExpired = 24 * 60 * 60 * 1000; // in 24 hours this cache entry expires completely
        final long softExpire = now + cacheHitButRefreshed;
        final long ttl = now + cacheExpired;

        Cache.Entry entry = new Cache.Entry();
        entry.etag = serverEtag;
        entry.softTtl = softExpire;
        entry.ttl = ttl;
        entry.serverDate = serverDate;
        entry.responseHeaders = headers;

        return entry;
    }

    /**
     * Parse date in RFC1123 format, and return its value as epoch
     */
    public static long parseDateAsEpoch(String dateStr) {
        try {
            // Parse date in RFC1123 format if this header contains one
            return DateUtils.parseDate(dateStr).getTime();
        } catch (DateParseException e) {
            // Date in invalid format, fallback to 0
            return 0;
        }
    }

    /**
     * Returns the charset specified in the Content-Type of this header,
     * or the HTTP default (ISO-8859-1) if none can be found.
     */
    public static String parseCharset(Map<String, String> headers) {
        String contentType = headers.get(HTTP.CONTENT_TYPE);
        if (contentType != null) {
            String[] params = contentType.split(";");
            for (int i = 1; i < params.length; i++) {
                String[] pair = params[i].trim().split("=");
                if (pair.length == 2) {
                    if (pair[0].equals("charset")) {
                        return pair[1];
                    }
                }
            }
        }

        return HTTP.DEFAULT_CONTENT_CHARSET;
    }
}